Russell King wrote:
> Indeed.  However, I don't believe user space should _rely_ on the flag.
> The reason is that there are network cards out there where the only way
> to get the link status _is_ to transmit a packet, even on 10baseT.
> 
> PCNET is one example - the "oh my god my link is down" status bit is in
> the transmit ring headers, not in an easily accessible register.
> 
> The only interpretation user space can place on IFF_RUNNING for these
> cards is that if its not set, packets will get dropped by the interface.
> If its set, packets _may_ be dropped by the interface.

These are the exception not the rule, though, so I don't think we should
design primarily for them.  On most decent cards, we can not only ask
for link status from a register, but also get interrupts when link
change occurs [though we may still need a timer for certain link
states].


> [note I've not found anything in 2.4.5 where netif_carrier_ok prevents
> the net layers queueing packets for an interface, and forwarding them
> on for transmission].

we want netif_carrier_{on,off} to emit netlink messages.  I don't know
how DaveM would feel about such getting implemented in 2.4.x though,
even if well tested.

Note we went over netif_carrier_xxx and related issues not a week ago,
IIRC

	Jeff


P.S. netdev@oss.sgi.com added to cc.  please cc there on net
interface/driver issues...

-- 
Jeff Garzik      | Andre the Giant has a posse.
Building 1024    |
MandrakeSoft     |
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